Both the promise and the challenge of distributed systems often derive from emergent behavior, functionality that is not defined explicitly in the individual components of the system but results from their interactions. Effective use of these systems depends on techniques for monitoring and controlling such system-level behavior. A fruitful source of inspiration for such techniques is statistical mechanics, with its mature success in explaining the macro-level characteristics of matter from the interactions of atoms and molecules. This paper summarizes a number of such analogies that we have exploited in our work.